14.5 Clinical notes and clinical testing Gag reflex Sensation supplied by the glossopharyngeal nerve is different in quality to that supplied by the trigeminal. Place a finger on the anterior part of the tongue (V) and then the posterior part (IX) to demonstrate this. The gag reflex is mediated by the glossopharyngeal (afferent limb) and the vagus (efferent limb). It is a functional test of both nerves.
The glossopharyngeal nerve (IX) 85Chapter 15 THE VAGUS NERVE (X) 15.1 Functions The main functions of the vagus are phonation and swallowing. It also transmits cutaneous sensory fibres from the posterior part of the external auditory meatus and the tympanic membrane.
It supplies the gut tube as far as the splenic flexure of the transverse colon (roughly), and the heart, tracheobronchial tree and abdominal viscera. These fibres, though, are by no means essential to life, whatever others may tell you, since they can be cut, as in vagotomy. And do you suppose heart surgeons reconnect vagal branches during transplant operations? Of course not.
15.2 Origin, course and branches (Fig. 15.1) The vagus is the most extensively distributed of all cranial nerves. Its name reflects both its wide distribution and the type of sensation it conveys (Latin: vagus
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